About 90% of people who develop cardiovascular disease have prior exposure to risk factors that could be targeted through lifestyle interventions. E-mail based walking programs that promote sustainable ecological supports for active lifestyles hold promise for cardiovascular disease risk-reduction, but few such programs have been developed or evaluated with objective outcomes. The purpose of this study is to conduct a randomized controlled trial to evaluate the effects of three walking programs: (1) Usual Care: walking information;(2) WalkLink: 16-week e-mail based walking program;and (3) WalkLink+: 16-week e-mail based walking program with ecological supports, among 220 sedentary adults with risk factors for cardiovascular disease recruited through primary care settings. Primary specific aims include: (1) To evaluate the effects of the three programs on change in aerobic fitness, blood pressure, body composition, body mass index, and moderate and vigorous walking and physical activity from baseline to posttest, and at 6-month follow-up;(2) To evaluate the effect of selected moderator/mediator variables on program outcomes, including: self-management skills (e.g., goalsetting, self-monitoring), social support (e.g., number of walking partners, social cues), and physical support (e.g., neighborhood walkability, physical cues). The proposed research builds upon an email-based walking program Dr. Rovniak previously conducted, and her current research in implementing ecological supports to promote physical activity, AIDS prevention and tobacco control. Candidate and Environment: Liza S. Rovniak received her Ph.D. in Clinical Health Psychology in 2003, and her MPH in Health Promotion and Behavioral Science in 2008, as part of her mentored K99 award. She proposes to conduct her ROO project at Penn State College of Medicine, where she has obtained a tenure-track Assistant Professor position in the Division of General Internal Medicine and Department of Public Health Sciences. Her goal is to develop an independent research career with emphasis on designing economically sustainable lifestyle change interventions to promote physical activity and reduce risk of cardiovascular disease.